This invention relates generally to the production of continuous glass fibers, and more particularly, to the winding of continuous glass fibers onto a cylinder (tube) to form a primary package of fiber.
In general, manufacturing process for producing and winding continuous glass fibers are known. Schematic representations of a typical example of such prior art processes are shown in FIGS. 1A and 1B. Respective continuous glass fibers 1002 are made by the rapid mechanical attenuation of molten glass exuding from a furnace through a bushing 1004 incorporating a large number of nozzles. During the fiber production process an individual fiber (filaments) 1002 exudes from each of the nozzles, to form two fans 1008 of filaments. The respective filaments of fans 1008 pass through a light water spray 1010 (FIG. 1A), over an applicator 1009 which transfers a protecting and lubricating "size" onto the filaments, and are then gathered by a suitably U-shaped shoe into a bundled strand of filaments 1012. Strand 1012 then passes to a winder 1014 which mechanically attenuates the strands 1012 and forms a package (cake) 1020 of continuous strand 1012.
Strands 1012 are wound about a rotating collet 1016 bearing a paper or plastic tube 1018. A predetermined amount of continuous strand 1012 is wound onto tube 1018 to form a cake 1020. A traverse 1019 is typically employed to lay successive lengths of a continuous strand 1012 onto tube 1018 at small angles to one another to facilitate subsequent unwinding of the fiber from the package.
Terminating the winding process to remove cake 1020 from the collet 1016 tends to be problematical. During the time period required to remove the cake 1020 from the collet and place a new tube 1018 on the collet 1016, molten glass continues to exude from each nozzle of bushing 1004. All of such exuded molten glass is wasted and must be removed for disposal before the winding process can be restarted.
To deal with this problem, automatic winders have been implemented with two alternately operable collets for winding continuous strands 1012. After a complete cake is wound on one collet, strand 1012 is transferred to and wound about the second collet, while cake 1020 is removed from the first. Referring to FIGS. 2A-2E, such a prior art automatic winder 1022 includes two collets 1028 and 1030, and a winding shield 1026, all mounted on a rotatable turret 1024. In operation, strand 1012 is wound about collets 1028 and 1030 on an alternating basis; turret 1024 is rotated to dispose first one and then the other collet to receive strand 1012. Shield 1026 serves to prevent debris such as water and lubricant (size) from being deposited on the inactive collet.
More particularly, referring to FIG. 2A, one of the collets, e.g., collet 1028, rotatable at a predetermined speed, is disposed to receive strand 1012. Strand 1012 is thus wound onto a tube supported by collet 1028. After a predetermined amount of continuous strand 1012 is wound onto the tube, a transfer of strand 1012 to the other collet leg, collet 1030, is effected. The transfer between collets involves a number of steps:
a mechanism pushes strand 1012 to the front of rotating collet 1028 beyond the lateral extent of shield 1026 to ensure that shield 1026 does not interfere with strand 1012 when turret 1024 is rotated; the inactive collet, e.g., collet 1030 is accelerated to full rotational winding speed; turret 1024 is rotated in a clockwise direction to a predetermined position at which strand 1012 is placed in contact with the feeding (forward) surface of collet 1030 (FIG. 2B); the rotational speed of collet 1028 is reduced, causing loop 1032 to form in strand 1012 between the collets (FIG. 2C); the size of loop 1032 increases until strand 1012 breaks and causes strand 1012 to become completely wrapped around the front end of collet 1030 (FIG. 2D) and begins to wind onto collet 1030; and the cake from collet 1028 is removed while strand 1012 is being wound onto collet 1030 (FIG. 2E).
A significant problem with such prior art is that strand 1012 frequently breaks before a successful transfer is made between collets. Accordingly, human intervention is required to restart the winding process, and, until the process is restarted, exuded molten glass is wasted.
A number of factors contribute to the breakage of strand 1012 during an attempted transfer between collets. A primary factor is the requirement that strand 1012 be forced to the front of the collets to clear shield 1026 during the transfer between collets. Another factor is that a typical automatic winder only has the ability to rotate turret 1024 in one direction between two index positions. This tends to restrict the ability by adjusting and optimizing the angle at which strand 1012 contacts the collets when a transfer is made.
Another problem which arises with many automatic winders is their inability to maintain a relatively constant distance between the traverse 1019 (FIG. 1) and the point at which strand 1012 engages cake 1020 as the diameter of the cake increases during the winding process. This tends to cause the tension in strand 1012 to change as the diameter of the cake increases and, in turn, varies the diameter of strand 1012 in relation to the cake diameter. This problem can also be attributed to limiting rotation of turret 1024 to a single direction and between two fixed index positions.
Thus, there remains the need for an automatic winder which reduces the frequency of strand breakage during the transfer of strands between winder collets, an improved winding shield, and an arrangement for providing selective bi-directional rotation of a turret.